Process for the recovery of organic acids from oxidized nonaromatic hydro carbons



Oct. 24, 1933. H. BELLER ET AL PROCESS FOR THE RECOVERY OF ORGANIC ACIDSFROM OXIDIZED NONAROMATIC HYDROCARBONS Filed 0G13. 2l. 1951 Tow M MJ E?KEEP# wm.. m nu By M gu Al Patented Oct. 24, 1933 UNITED STATES PATENTOFFICE PROCESS FOR THE RECOVERY OF ORGANIC ACIDS FROM OXIDIZEDNONAROMATIC HYDROCARBONS Application October 21,1931, Serial No.570,128, and in Germany October 22, 1930 6 Claims.

The present invention relates to improvements in the recovery of organicacids from products of the destructive oxidation of liquid and solid,non-aromatic hydrocarbons.

It is already known that the destructive oxidation of non-aromatichydrocarbons, such as mineral oil, paraffin wax, parailin oil or oilscontaining the same, with the aid of oxygen, air or other oxygen bearingoxidizing agents at temperatures between about 130 and 180 C. resultsnot only in acid products containing oxygen, as for example carboxylicacids and hydroxy-carboxylic acids, but also greater or less amounts ofneutral compounds containing oxygen, such as alcohols, aldehydes,ketones, esters, laetones, estolides, lactides, aldehyde-alcohols andketone-alcohols. In order to recover the valuable acid constituents,especially those which are present in the combined or modified form,namely esters and estolides, it has beenv necessary hitherto to saponifythe oxidation product with caustic alkalies or oxides or hydroxides ofthe alkaline earth metals.

We have now found that the organic acids, especially those present inthe combined or modified form as esters, estolides, lactones andlactides, are recovered in an advantageous manner from products of thedestructive oxidation of liquid to solid non-aromatic hydrocarbons bytreatingthe oxidation products in a closed vessel and at a temperature,which is at least 75 C. but is always kept below the boiling temperatureof water at the pressure employed, which is produced both by heating andby the evolution of carbon dioxide, with an aqueous solution of anamount of alkali metal carbonate, as for example sodium, potassium orammonium carbonate, at least corresponding to the .saponiiication valueof the oxidation product, preferably in excess thereof, the resultingalkali metal salts being worked up into free fatty acids byacidification after the removal of the unsaponiable constituents.Contrary to expectation, not only the free carboxylic acids but alsothose which are present in the oxiv dation products in a combined form,such as (Cl. 26o-116) temperature, especially those above 100 C., withthe simultaneous. employment of elevated pressure. When working in thismanner more carboxylic acids are obtained from the reaction mixture whenworking up the reaction mixture than corresponds to the' acid value ofthe oxidation product employed.

The amount o1 alkali metal carbonate (which term is intended to includeammonium carbonate) is preferably calculated on the saponification valueof the oxidation product, which is usually considerably greater than, asfor example twice as great as, the acid value. It is, however,advantageous to use an amount of alkali carbonate slightly in excess, asfor example from about 5 to about 10 per cent in excess, of the amountso calculated for complete saponiiication. Still higher quantities maybe employed but an excess of more than 10 per cent is superuous andunduly expensive. The alkali carbonate can be employed in the form offrom 5 per cent aqueous solutions to hot saturated solutions and ispreferably employed in the form of an about 20 per cent aqueoussolution, the product to be saponiiied being slowly introduced into thehot solution of carbonate. At the commencement of the treatment thetemperature is kept usually between and 100 C., preferably between aboutand about 95 C., until the 'greater part of the carbon dioxide formed bythe conversion of the free carboxylic acids present has been evolved.Towards the end of the reaction, the temperature is preferably raisedabove 100 C. up to say 350 C., generally, however, to from about 160 toabout 185 C., and the pressure increased above l'atmosphere, usuallyfrom 8 to 9 atmospheres, or even to 15 or more atmospheres. Care shouldbe taken for a uniform removal of the carbon dioxide evolved. It is ofspecial advantage thoroughly to mix the reaction mass during thetreatment, as for example by means of a highspeed stirrer. For example,the saponiiication may be carried out in a turbo-mixer or vesselprovided With turbo-stirrers, in which process the time required forsaponiflcation is very short. By suitable arrangement of the inlet andoutlet devices and by continuous withdrawal of the saponified productwhile introducing fresh initial material, the saponiiication in theturbo-mixer may readily be rendered continuous. Processes for carryingout the saponication are further illustrated by the diagrams in Figures1 and 2 annexed hereto, Figure 1 showing continuous working in a directilow and Figure 2 showing a modification of this process in which thefinal saponiication may be carried out in a cycle.

When the saponication is completed the unsaponiable constituentsseparate out from the soap solution, if necessary after diluting thereaction product with water, when a concentrated carbonate solution hasbeen used for the reaction, as the upper layer which is removed. Anyremaining unsaponiable constituents in the solution may be completelyremoved by extraction with organic solvents, as for example gasoline,carbon tetrachloride, other chlorinated hydrocarbons and ethyl ether. Ifdesired, the unsaponiilable constituents may be subjected lto oxidationagain, if necessary after washing for a short time with dilute alkalicarbonate solution or water in order to remove small quantities of soapcontained therein.

The following examples will further illustrate the nature of thisinvention, but the invention is not restricted to these examples.

Eample 1 100 kilograms of a crude oxidation product having an acid valueof 100 and a saponifcation value of 150, obtainable by the destructiveoxidation of hard paraiiin wax by blowing it for several hours with airat about 150 C. in the presence of 0.1 per cent by weight of the wax ofsodium carbonate in the form of a concentrated aqueous solution, isallowed to ow in a thin stream at C. into a solution of 15.6 kilogramsof anhydrous sodium carbonate in '70 kilograms of Water while stirringvigorously under atmospheric pressure. AfterY the initial turbulentevolution of carbon dioxide has ceased, the mixture is transferred to astirring autoclave and further treated for about an hour at 120 C.,whereby the carbon dioxide set free is removed by frequently releasingthe pressure in the autoclave down to 3 atmospheres. The soap solutionobtained is diluted with water and extracted with benzine. Thenbyacidication with sulphuric acid about 50 kilograms of pure fatty acidsare obtained.

Example 2 100 kilograms of an oxidation product having an acid value of'75 and a saponification value of 140 and obtained from soft paraiiinwax by blowing it for several hours with air at about 150 C. are stirredtogether with a solution of 14.3 kilograms of anhydrous sodium carbonatein 60 kilograms of water at about C. under atmospheric pressure. Afterthe initial turbulent evolution of carbon dioxide has ceased, themixture is charged several times at 170 C. through a turbomixer (3000revolutions per minute) provided with a circulating vessel, whereby apressure of about 9 atmospheres is maintained. After a few minutes thesaponication is almost completely effected and the treatment isterminated after about 15 minutes. The reaction mixture is worked upinto free fatty acids in the manner described in Example 1.

What we claim isz- 1. In the separation of organic acids from productsof the destructive oxidation of from liquid to solid, non-aromatichydrocarbons, the step which comprises heating such oxidation product ina closed, pressure-tight vessel to a temperature between 75 C. and thebc-iling point of water at the pressure employed together with an atleast 5 per cent aqueous solution of a quantity of an alkali metalcarbonate at least corresponding to the saponication value of saidoxidation product.

2. In the separation of organic acids from products of the destructiveoxidation of from liquid to solid, non-aromatic hydrocarbons, the stepwhich comprises heating such oxidation product in an open vesseltogether with an at least 5 per cent aqueous solution of a quantity ofan alkali metal carbonate at least corresponding to the saponicationvalue of said oxidation product, to a temperature below the boilingpoint of water until the evolution of carbon dioxide has ceased and thenheating the whole in a closed pressure-tight vessel to a temperaturebetween 75 C. and the boiling point of water at the pressure employed.

3. In the separation of organic acids from products of the destructiveoxidation of from liquid to solid, non-aromatic hydrocarbons, the stepwhich comprises heating such oxidation product in an open vesseltogether with an at least 5 per cent aqueous solution of a quantity ofan alkali metal carbonate at least corresponding to the saponicationvalue of said oxidation product, to a temperature below the boilingpoint of water until the evolution of carbon dioxide has ceased and thenheating the whole in a pressure-tight turbomixer to a temperaturebetween 100 C. and the boiling point of water atv the pressure employed.

4. In the separation of organic acids from products of the destructiveoxidation of parailin wax, the step which comprises heating suchoxidation product in an open vessel to a temperature between 60 and 95C. with an at least 5 per cent aqueous solution of a quantity of analkali metal carbonate at least corresponding to the saponificationvalue of said oxidation product until the evolution of carbon dioxidehas ceased and then heating the whole in a closed, pressure- .tightvessel to a temperature between 100 and about 185 C.

5. In the separation of organic acids from products of the destructiveoxidation of parafn wax, the step which comprises heating such oxidationproduct in an open vessel to a temperature between about 60 and about 95C. with an aqueous solution of a quantity of sodium carbonate, exceedingthat theoretically required for complete saponication by from about 5 toabout 10 per cent, until the evolution of carbon dioxide has ceased andthen heating the whole in a closed, pressure-tight vessel to atemperature between 100 and about 185 C.

6. In the separation of organic acids from products of the destructiveoxidation of parain wax, the step which comprises heating such oxidationproduct in an open vessel to a temperature between about 60 and about 95C. with a quantity of an about 20 per cent aqueous solution of sodiumcarbonate, exceeding that theoretically required for completesaponication by from about 5 to about 10 per cent, until the evolutionof carbon dioxide has ceased, and then heating the whole in a closed,pressure-tight vessel to a temperature between 100 and about 185 C.

HANS BELLER. MARTIN LUTHER.

